I did see an SP unit once that had both - quite impressive even in the daylight. KCS also had both on some units -saw one of those at night.

What you are talking about at Mars light (Mars Signal Light Co?) and Gyralites (Pyle National) who both made several styles, some are obvious as to the manufacture while some versions are so similar that the differences are subtle. Mars usually had a figure 8 pattern, whereas the Gyralite had a flattened circle (think flat tire).

Most of the later SP units used Gyralites, but the very last units used Oscitrol(?) units which had two fixed bulbs one aimed to the right and one to the left that alternated flashing. ICG also used the Oscitrols.

The Mars and Gyralights have a motor and gearbox that rotates the mounting for the sealed beams, which is an additional maintenance item. (I think the original bulb and reflector types actually moved the reflector.) The failed SPSF merger was the beginning of the end with SP adopting the yellow solid state beacon that ATSF used instead of gyralights that carried into the early new/rebuilt units with ditch lights.

I consider the failed SPSF merger and removal of ditchlights the beginning of the end of the SP.